1. Field
The presently disclosed subject matter relates generally to devices, systems and methods used to replace and/or support a portion of a skeletal structure, and more particularly to devices, systems and methods used to support the spine after removal of at least a part of a vertebra or vertebrae.
2. Description of the Related Art
When a vertebra is damaged, malformed, or diseased, surgery may be used to replace the vertebra or a portion thereof with a prosthetic device to restore spinal column support. For example, vertebral body replacement is commonly used in the treatment of vertebral fracture, tumor, infection, misconfiguration/deformity or other problems or diseases.
In recent years, several artificial materials and implants have been developed to replace the vertebral body, such as, for example, titanium cages, ceramic, ceramic/glass, plastic or PEEK, and carbon fiber spacers. Various expandable prosthetics or expandable cages have also been developed and used for vertebral body replacement. The expandable prosthetic devices are generally adjustable to the size of the cavity created by various procedures, such as a corpectomy procedure. The prosthetic devices are also typically at least partially hollow to accommodate bone cement, bone infusion materials, bone fragments, or other regenerative material to facilitate fusion in vivo. Some expandable prostheses may be adjusted prior to insertion into the cavity, while others may be adjusted in situ. An expandable prosthetic device that is adjustable in situ can provide an optimal, tight fit by in vivo expansion of the device. Some other benefits offered by an expandable prosthetic device are that they can facilitate distraction across the resected vertebra, and allow immediate load bearing after corpectomy.
Instrumentation and specialized tools for insertion of a vertebral implant is one important design parameter to consider when designing a vertebral prosthesis. Spinal surgery procedures can present several challenges because of the small clearances around the prosthetic when it is being inserted into position. Another important design consideration includes the ability of the device to accommodate various surgical approaches for insertion of the vertebral implant.
Techniques, instrumentation and implants have changed over the years and have been better adapted to address many forms of spinal injury and deformities that can occur due to trauma, disease or congenital effects. One type of spinal deformity, a kyphosis, involves a prolapse of the vertebral column towards the front of the body, often caused by the destruction of the vertebral body itself. This destruction can be in the form of a trauma type injury, such as a fracture or burst injury to the vertebral body, or a non-traumatic deformity caused by a tumor or a degeneration of the bone in the vertebral body.
Treatment of a kyphosis in the thoracic or lumbar spine appears now to be best achieved through an anterior approach, particularly in order to avoid some of the more severe complications associated with support or replacement of a damaged vertebral body. In most treatments of a kyphosis, a high degree of anterior reconstruction of the spine is required, most frequently involving total removal of the damaged vertebral body. In a typical anterior approach, partial or total ablation of the vertebral body and the two adjacent vertebral disks is carried out. The remaining space is then distracted to manipulate the spine to its correct orientation.
In some cases, the remaining space is filled with a polymerizable paste or a bone graft which is frequently modeled to give it the shape of the destroyed vertebral body. Frequently, autologous bone, such as that extracted from the ilium, is used to bridge the remaining space. The polymerizable paste can include a PMMA bone cement. Once the space remaining after the removal of the original vertebral body has been filled, an osteosynthesis instrument is positioned between the adjacent unaffected vertebrae to prevent any relative movement therebetween. The osteosynthesis device restabilizes the vertebral column, to support the loads to which the thoracic or lumbar spine is exposed, and to enhance the likelihood and quickness of union of the bone graft material with the adjacent vertebral bodies. Once the bone graft and material is sufficiently solid, the osteosynthesis device normally is not burdened with carrying the primary loading forces or enduring the primary mechanical stresses.
Another variety of implant devices particularly suited for replacement of vertebral bodies include components of generally solid construction which completely occupy the empty vertebral space. Such implants include vertebral prosthesis which include some feature for expansion of the device in situ.
In recent years, the application of anterior approaches to instrumenting the spine has become more prevalent. As these anterior approaches advance, vertebral body replacements that are specifically designed to enjoy all of the benefits of anterior surgery.